The present invention relates generally to rotary transformers. More specifically, the present invention relates to mechanisms for positioning the rotor of a rotary transformer relative to a rotor stack mounted on a common rotatable shaft. A corresponding operating method is also disclosed.
The present application is based on Japanese Patent Application No. 2002-099827, which application is incorporated in its entirety by reference.
Rotary transformers are conventional devices that have been employed for routing input and/or output signals in commonly known devices such as resolvers, synchros, etc. In the discussion that follows, the application of rotary transformers to resolvers will be described. It will be appreciated that a resolver is basically a rotary, electromechanical device used to perform trigonometric computations by varying the magnetic couplings between its primary and secondary windings. One example of such a device is disclosed in Japanese Unexamined Patent Application Publication No. S63-318725, which is also incorporated herein by reference.
FIG. 4 illustrates the employment of a rotary transformer in conjunction with a resolver. More specifically, FIG. 4 is a partial cross-sectional view of a conventional resolver employing a rotary transformer, in which a circular case 401 encloses a resolver 402 and a rotary transformer 403. The resolver 402 includes a resolver stator 405, which has a resolver stator winding 404; the rotary transformer 403 includes a stator transformer 407, which has a stator transformer winding 406. Both the resolver stator 405 and the stator transformer 407 are disposed adjacent to the case 401. A shield plate 9a that prevents leakage of magnetic flux from the stator transformer 407 of the rotary transformer 403 is disposed between the resolver stator 405 and the stator transformer 407. The rotary transformer 403 provides current to the resolver 402 and permits signal input and output.
In addition, the resolver includes a resolver rotor 411, which has a resolver rotor winding 410, while the rotary transformer 403 includes a rotor transformer 413, which has a rotor transformer winding 412. Both the resolver rotor 411 and the rotor transformer 413 are coupled to a rotary shaft (not shown), which shaft permits both the resolver rotor and the rotor transformer to rotate freely within case 401.
It will be noted that the resolver stator 405, stator transformer 407, resolver rotor 411 and rotor transformer 413 are each fabricated from stacks of cut, solid steel bars. It will also be noted from FIG. 4 that the stator transformer 407 is fixed with respect to the side of the case 401 by a retaining ring 460, i.e., a “C” ring. Finally, it should be noted that the resolver rotor winding 410 is connected from the rotary transformer winding 412 via a crossover (not shown in FIG. 4).
It will be appreciated that the output of the resolver rotor winding 410 is determined by the number of magnetic poles, the phase of the drive voltage, etc. When the resolver rotor 411 is secured to the rotary shaft (not shown in FIG. 4), the output of the resolver rotor winding 410 is uniquely determined with respect to the rotary shaft. On the other hand, the rotor transformer winding 412 of the rotary transformer 403 is connected to the resolver rotor winding 410 via a pair of crossover leads (hereinafter simply crossover). While the length of the crossover is constant, if the position of the rotor transformer winding 412 on the rotary shaft is not taken into account, the distance between the rotor transformer winding 412 and the resolver rotor winding 410 will vary. Thus, the crossover may come into contact with the stator transformer 407, the resolver stator 405, etc., resulting in a short circuit.
In order to prevent this type of problem from occurring, it is desirable that the output leads of the rotor transformer winding 412 and the resolver rotor winding 410 be adjacent to one another. However, since the rotor of the rotary transformer and the rotor of the resolver are normally manufactured separately, the rotor transformer winding 412 and resolver rotor winding 410 are also independently wound. Therefore, in order to make the output leads of the rotor transformer winding 412 and the resolver rotor winding 410 (collectively the crossover) mutually adjacent during assembly, they must be positioned visually. It will be appreciated that this is an obstacle to the mass production, i.e., automation of the manufacturing process, of resolvers, etc.
What is needed is a positioning mechanism that permits automation of the winding and assembly of multiple electrically coupled rotor transformers on a common rotary shaft. It would be particularly desirable if the positioning mechanism were an integral part of one of the rotor transformers, e.g., the rotor of a rotary transformer. What is also needed is a mechanism for routing the crossover that does not adversely influence the flux profile of the rotary transformer.